1. Field of the Invention
The present invention relates to a method for manufacturing a multilayer ceramic board.
2. Description of Related Art
As for a method for manufacturing a multilayer ceramic board, a so-called non-contraction process is known wherein a contraction prevention layer whose principal component is alumina or the like is adhered to both upper and lower both principal surfaces of an unbaked multilayer ceramic member formed by layering a ceramic green sheet that can be baked at a low temperature and a wiring conductor made up of a low melting point metal, and these are baked at the baking temperature of a multilayer ceramic member, following which an unsintered contraction prevention layer is removed (e.g., see Japanese Unexamined Patent Application Publication No. 4-243978.
A technique for forming a protrusion on the principal surface of a multilayer ceramic board fabricated with the non-contraction process has been disclosed in Japanese Unexamined Patent Application Publication No. 2001-111223. This protrusion can be used as a spacer at the time of mounting an electronic component, such as reinforcing a via hole conductor protruding on the principal surface of a multilayer ceramic board, or forming it as a rib-like protrusion, so as to prevent the outflow of resin or solder, or to serve as the side wall of a cavity.
According to a non-contraction process, contraction in the planar direction (X-Y direction) perpendicular to the layering direction (Z direction) can be prevented, whereby a multilayer ceramic board having high dimensional accuracy can be fabricated.
However, although such a multilayer ceramic board having high dimensional accuracy can be fabricated, in the event of forming a wiring conductor on the surface of this board, the wiring conductor is formed in a state of protruding from the board surface, resulting in a problem wherein the wiring conductor of the board surface becomes separated due to wear.
Also, with the multilayer ceramic board described in Japanese Unexamined Patent Application Publication No. 2001-111223, there is a disclosure regarding a wall-like protrusion being formed, but this protrusion is only formed inside the outer circumference of the board, and accordingly, there is a problem wherein the portion of the board surface side where a wiring conductor can be formed is narrow.